1. Field of the Invention
The present invention relates to a vacuum circuit breaker disposed so as to be fixed inside a switchgear, a vacuum circuit breaker contact slow closing method, and a contact erosion measuring method and contact gap length setting method using that slow closing method.
2. Description of the Related Art
In conventional gas-insulated cubicles, withstand voltages of contacts of vacuum interrupters disposed in sulfur hexafluoride (SF6) gas have hitherto been examined by setting the contacts to a predetermined gap length manually.
In slow closing methods in these conventional gas-insulated cubicles, the gap length of the contacts has been set to a predetermined value by moving a plunger of an electromagnetic apparatus for closing the contacts of the vacuum interrupter using a manually-operated handle and interposing a spacer between an opening and closing lever and a damper operating interdependently with the movement of the plunger. (See Patent Literature 1, for example.)
In these conventional slow closing methods, because the spacer is slid between the opening and closing lever and the damper by pressing a push button mounted to the spacer, the spacer can be interposed between the opening and closing lever and the damper by an external push-button operation, making the operation of mounting the spacer safer. Because a resetting spring is interposed between the push button and a guiding frame for the push button, the spacer is withdrawn from between the opening and closing lever and the damper automatically after a withstand voltage test by ceasing to press the push button, making the operation of removing the spacer safer. In addition, because a pin is disposed so as to protrude from the opening and closing lever and a securing portion is formed on the spacer such that the pin is engaged in the securing portion when the spacer is interposed between the opening and closing lever and the damper, it is possible to leave the push button pressed, enabling the withstand voltage test to be executed more safely.
Patent Literature 1: Japanese Patent Laid-Open No. HEI 11-86696 (Gazette)
Conventional vacuum circuit breaker slow closing methods have the following problems:
(1) Because the gap length is set by interposing the spacer between the opening and closing lever and the damper, fine adjustment of the gap length is not possible;
(2) Because the contacts are moved by a lever principle using a manually-operated handle, workability is reduced when setting the gap length;
(3) Specialized equipment is required when performing slow closing, increasing costs; and
(4) The construction of an operating mechanism portion is complicated, making workability poor in slow closing methods in which the operating mechanism portion is operated.